Bacitracin is an antibiotic of relatively limited human therapeutic application, namely primarily topical usage. It is an excellent feed supplement for disease prevention and treatment as well as a growth promoter, and is extensively used in its relatively stable form, zinc bacitracin, as an additive to livestock feeds, as for pigs and cattle, and to poultry feeds. Because of its limited human antibiotic utility zinc bacitracin is to be preferred as an animal feed supplement for livestock and poultry.
Zinc bacitracin has been developed as a feed supplement because of its relatively greater stability in the face of elevated temperatures and moisture than bacitracin, see U.S. Pat. No. 2,809,892 issued Oct. 15, 1957 to Francis W. Chornock. However, commercial feed grade zinc bacitracin does not have an altogether satisfactory commercial stability to temperature and moisture. Efforts to improve the stability of bacitracin compositions have included the addition of lignins to form complexes, see U.S. Pat. No. 3,035,919 issued May 22, 1962 to Jack Ziffer et al., or the addition of insoluble zinc salts such as zinc oxide, see U.S. Pat. No. 3,025,216 issued Mar. 13, 1962 to Jack Ziffer et al.
George Hines of Commercial Solvents Corporation of Terre Haute, Indiana, the manufacturer of the commercial feed supplement called "BACEFIRM", which is zinc bacitracin, has summarized the stability of this material in an article entitled "Bacifirm (Zinc Bacitracin) In Liquid Feed Supplements" which was published in the AFMA Liquid Feed Symposium Proceedings by the American Feed Manufacturers Association, 53 W. Jackson Boulevard, Chicago Ill. 60604, in 1972.
Notwithstanding extensive research, the prevention of the decomposition of zinc bacitracin, particularly when used in conjunction with animal feeds containing a variety of fats, vitamins, minerals, drugs such as coccidiocides, etc. is not well understood. While there has been an improvement in the stability of commercially available feed grade zinc bacitracin during the past decade, instability problems of this material, particularly in the presence of temperature and moisture, and in the presence of widely used animal feeds, still exist.
I have determined that admixture of zinc bacitracin with animal feeds promotes the decomposition of the zinc bacitracin, particularly when the animal feed-zinc bacitracin mixture is mechanically mixed and/or heated.